Room-Temperature Epitaxial Electrodeposition of Single-Crystalline Germanium Nanowires at the Wafer Scale from an Aqueous Solution

Direct epitaxial growth of single-crystalline germanium (Ge) nanowires at room temperature has been performed through an electrodeposition process on conductive wafers immersed in an aqueous bath. The crystal growth is based on an electrochemical liquid-liquid-solid (ec-LLS) process involving the electroreduction of dissolved GeO2(aq) in water at isolated liquid gallium (Ga) nanodroplet electrodes resting on single-crystalline Ge or Si supports. Ge nanowires were electrodeposited on the wafer scale (>10 cm(2)) using only common glassware and a digital potentiostat. High-resolution electron micrographs and electron diffraction patterns collected from cross sections of individual substrate-nanowire contacts in addition to scanning electron micrographs of the orientation of nanowires across entire films on substrates with different crystalline orientations, supported the notion of epitaxial nanowire growth. Energy dispersive spectroscopic elemental mapping of single nanowires indicated the Ga(l) nanodroplet remains affixed to the tip of the growing nanowire throughout the nanowire electrodeposition process. Current voltage responses measured across many individual nanowires yielded reproducible resistance values. The presented data cumulatively show epitaxial growth of covalent group IV nanowires is possible from the reduction of a dissolved oxide under purely benchtop conditions.